1. Field of the Invention
The present invention relates generally to automotive external lighting systems. More particularly, the present invention relates to an automotive external lighting system using pulse width modulation to drive a single filament for multiple signaling purposes.
2. Discussion
External lighting systems have been used with automobiles for many years, and continue to increase in complexity and sophistication. Such systems are used for turn signaling as well as park signaling, and generally must abide by strict industry standards. Typical industry standards specify vibration, moisture, dust, corrosion, and photometry limits. For example, it is common for photometric requirements to detail minimum illumination intensity for parking and turning functions. Thus, when a vehicle is indicating a change in direction via a flashing turn signal, a corresponding brightness must be produced so that nearby vehicles and pedestrians are adequately put on notice. Similarly, park signaling systems for clearance purposes (indicating overall width and height of the vehicle) or side marker purposes (indicating overall length of the vehicle) have corresponding required brightness levels.
Typically, turn signaling requires higher brightness levels than park signaling, due to the increased concern for safety. As a result, conventional lamps for automotive external lighting systems include a major filament and a minor filament. The major filament is used for turn signaling, whereas the minor filament is used for park signaling. A separate connection mechanism is therefore provided to each filament and a control circuit determines which filament to illuminate. A shortcoming with this approach, however, is the fact that two wires must be employed as a connection mechanism. This increases the number of parts and adds to the overall cost of the vehicle. Similarly, using multiple filaments requires more expensive lamps. It is therefore desirable to provide a system and method for producing external illumination with a single wire and lamp filament.
Conventional lighting systems also lack the ability to provide a variable brightness signal which can be customized to the particular vehicle size and photometry standards. For example, it is not uncommon for typical control circuits to provide a maximum of two current levelsxe2x80x94one for energization of the major filament, and the other for energization of the minor filament. This has substantially limited the flexibility of external lighting systems and caused a corresponding increase of design, manufacturing and maintenance costs. It is therefore desirable to provide an automotive external lighting system that operates on a variable brightness signal such that flexibility is increased.
In accordance with the present invention, an automotive external lighting system includes a control circuit for generating a variable brightness signal based on a predetermined brightness level, and an external lamp for producing external illumination based on the brightness signal. A connection mechanism electrically connects the control circuit to the external lamp. In a preferred embodiment, the brightness signal is a pulse width modulated signal, and the control circuit includes a microprocessor for generating the pulse width modulated signal. The control signal also includes a driver for driving the lamp in response to the pulse width modulated signal.
Further in accordance with the present invention, a method for producing external illumination for an automobile includes the step of generating a pulse width modulated signal based on a predetermined brightness level. The pulse width modulated signal is electrically connected to an external lamp of the vehicle, and external illumination is produced based on the pulse width modulated signal.
Further areas of applicability of the present invention will become apparent from the detailed description provided herein. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.